1. Field of the Invention
The present invention relates to ink jet recording heads used for ink jet recording apparatuses.
2. Description of the Related Art
An example of typical recording apparatuses is an ink jet recording apparatus that performs recording by discharging ink to a recording medium.
Such an ink jet recording apparatus generally includes a recording head provided with discharge ports for discharging ink. To discharge ink, a piezoelectric element or the like may be used for discharging ink, or an electrothermal transducer such as a heating resistor may be used for heating and discharging ink by an action of film boiling.
FIG. 13 is a perspective view showing a recording element substrate 1100 of a recording head provided with an electrothermal transducer. The recording element substrate 1100 is embedded in a recording head 1001. FIG. 14 is a cross-sectional view taken along a line XIV-XIV shown in FIG. 13. FIG. 15 is a cross-sectional view taken along a line XV-XV shown in FIG. 13. For convenience of description, a sealant for sealing the periphery of the recording element substrate 1100 is not illustrated in FIG. 13. In this example shown in the drawings, the recording head 1001 includes a first plate 1200, the recording element substrate 1100, a second plate 1400, and an orifice plate 1111. The first plate 1200 has an ink supply path 1202 for supplying ink to the recording element substrate 1100. The recording element substrate 1100 is supported on the first plate 1200 and fixed thereto such that the ink supply path 1202 communicates with an ink supply port 1102 of the recording element substrate 1100. The second plate 1400 has an opening for surrounding the recording element substrate 1100 and is supported on the first plate 1200, to fix a wiring substrate 1300. The orifice plate 1111 has discharge ports, and is fixed to the recording element substrate 1100 such that the discharge ports communicate with the ink supply port 1102 of the recording element substrate 1100. With such a recording head, the periphery of the recording element substrate 1100 is sealed with a sealant. For example, an end of the recording element substrate 1100 without protection treatment is sealed with a first sealant 1307. This prevents the end from being exposed to ink, thereby preventing the end from being corroded by the ink. In addition, as shown in FIG. 15, lead terminals 1302 that connect the wiring substrate 1300 and bumps 1105 provided on the recording element substrate 1100 are covered with a second sealant 1308. Accordingly, the lead terminals 1302 may be prevented from being corroded by ink, and lead wires may be prevented from being disconnected by an external force.
Meanwhile, an ink jet recording device has a recording characteristic recovery unit (hereinafter, also referred to as a recovery unit). In the ink jet recording apparatus, extremely small ink droplets (ink mist) are generated when ink is discharged from the discharge ports. The ink droplets may adhere to a discharge port side of the recording head (i.e., a surface where the discharge ports are made), or dust particles like those from paper may adhere to the discharge port side. Such an adhering matter may cause defective discharge of ink, thus degrading the quality of recording. To remove dust particles etc. adhering to the discharge port side, the recovery unit is generally used. The recovery unit uses a wiper made of an elastic material such as rubber, to wipe the discharge port side of the orifice plate 1111 and remove the ink droplets, dust particles, and the like.
FIGS. 16 and 17 are illustrations showing recovery processing at a discharge port side of a conventional recording head. FIG. 16 is a cross-sectional view showing the recording head during the recovery processing taken along a line XV-XV shown in FIG. 13. FIG. 17 is a cross-sectional view showing the recording head during the recovery processing taken along a line XIV-XIV shown in FIG. 13. A wiper 2500 moves on the discharge port side from the left side to the right side as shown in FIG. 16, or toward the far side in the longitudinal direction of the orifice plate 1111 as shown in FIG. 17, so as to wipe the discharge port side of the orifice plate 1111. Accordingly, the ink droplets and dust particles adhering to the discharge port side can be removed. At this time, the wiper 2500 contacts and wipes the discharge port side with a predetermined pressure by utilizing the elasticity of the wiper 2500, thereby removing the ink droplets and dust particles.
However, the stress of the sealant may cause a problem in relation to the wiper used during the wiping. In particular, a certain amount of sealant is necessary to be provided to attain the above-mentioned function. As shown in FIG. 17, a width W1 of the wiper 2500 is sufficiently larger than a width W2 of the recording element substrate 1100 in view of the manufacturing accuracy of the wiper 2500, the assembly accuracy of the wiper 2500 to a main body of the ink jet recording apparatus, the operation accuracy of the wiper 2500 during the wiping, etc. Owing to this, to prevent the wiper 2500 from contacting the wiring substrate 1300, a width W3 of the opening of the wiring substrate 1300 (or a width of an opening of the second plate 1400) to which the recording element substrate 1100 is mounted becomes sufficiently large. In such a case, to attain the function of the sealant, a relatively large amount of sealant is applied to the periphery of the recording element substrate 1100. Unfortunately, when selecting a sealant exhibiting a high adhesiveness with respect to a plurality of members, the choices are limited to a sealant whose internal stress is large after being cured, or one with a large coefficient of linear expansion. Such a sealant whose internal stress is large after being cured, or one with a large coefficient of linear expansion may cause an external force to be applied to the recording element substrate due to expansion and contraction of the sealant according to temperature change during a manufacturing procedure, or temperature change under an operating environment of a product. Due to this, the recording element substrate 1100 may become cracked.
In addition, a certain amount of sealant is necessary to prevent the upper edge of the recording element substrate 1100 from being exposed. This may also cause the recording element substrate 1100 to become damaged due to the internal stress of the sealant.